ChemInform Abstract: TOLUENE-3,4-DITHIOL (H2TDT) COMPLEXES OF GROUP 5A HALIDES. OBSERVATIONS OF LONE-PAIR STEREOCHEMICAL ACTIVITY AND REDOX BEHAVIOR. CRYSTAL AND MOLECULAR STRUCTURES OF (ASCL(TDT)) AND (PPH4)(SB(TDT)3)

1985 ◽  
Vol 16 (18) ◽  
Author(s):  
J. M. KISENYI ◽  
G. R. WILLEY ◽  
M. G. B. DREW ◽  
S. O. WANDIGA
Keyword(s):  
Lone Pair ◽  
Molecular Structures ◽  
Redox Behavior ◽  
Crystal And Molecular Structures ◽  
Stereochemical Activity

The crystal and molecular structures of the ligand (E)-Pyridine-2-carbaldehyde Pyridin-2'-ylhydrazone and the palladium(II) complex Chloro[(E)-pyridine-2-carbaldehyde pyridin-2'-ylhydrazonato]palladium(II) which involves the coordination of the ligand in its anionic form

1984 ◽  
Vol 37 (4) ◽  
pp. 739 ◽  
Author(s):  
AT Casey ◽  
BF Hoskins ◽  
IP Traverso
Keyword(s):  
Least Squares Method ◽  
Complex Structure ◽  
Lone Pair ◽  
Unit Cell ◽  
Molecular Structures ◽  
Thermal Parameters ◽  
Anionic Form ◽  
Hydrogen Atoms ◽  
Space Group ◽  
Crystal And Molecular Structures

The crystal and molecular structures of the ligand (E)-pyridine-2-carbaldehyde pyridin-2'-ylhydrazone hydrate and its complex chloro[(E)-pyridine-2-carbaldehyde pyridin-2'-ylhydrazonato]palladium(II) have been determined by single-crystal three-dimensional X-ray diffraction techniques. Crystals of the ligand are monoclinic with space group P 21/c. The unit cell, which contains four molecules of ligand together with approximately ten disordered water molecules, has the dimensions a 17.762(4), b 3,8717(11), c 18.503(4) Ǻ and β 107.99(2)°. Crystals of the complex are triclinic with space group P1, and the unit cell has the dimensions a 6.9721(3), b 9.0739(11), c 9.1304(9) Ǻ, α81.116(9), β 88.778(8) and γ 81.392(8)°; Z = 2. The ligand structure was solved by direct methods and refined with anisotropic thermal parameters for all non-hydrogen atoms and isotropic thermal parameters for hydrogen and solvent atoms. The complex structure was solved by conventional Fourier methods and refined with anisotropic thermal parameters for all non-hydrogen atoms. A full-matrix least-squares method was employed for both structures based on 1295 and 2224 statistically significant reflections giving final values of R 0.061, Rw 0.068 and R 0.028, Rw 0.030 for the ligand and complex respectively. The structure analysis of the ligand shows definite evidence of delocalization of lone pair electrons in the hydrazine moiety. The ligand in its anionic form coordinates in a tridentate manner to the palladium atom in the complex through the two pyridine nitrogen atoms and the distal nitrogen of the hydrazine residue. A square-planar array is formed by a chlorine atom occupying the fourth position. Molecular dimensions suggest that the lone pair on the proximal nitrogen is delocalized over the entire molecule. Standard valence-bond and 'increased valence' methods have been applied in order to determine resonance schemes consistent with the observed structures of both the ligand and its complex.

Cis-trans-Isomere von Diazadiphosphetidin-Derivaten: Fünf Kristall- und Molekülstrukturen / Cis-trans Isomers of Diazadiphosphetidine Derivatives: Five Crystal and Molecular Structures

1979 ◽  
Vol 34 (2) ◽  
pp. 256-261 ◽  
Author(s):  
Siegfried Pohl
Keyword(s):  
Single Crystal ◽  
Crystal Structures ◽  
Lone Pair ◽  
Molecular Structures ◽  
Trans Isomers ◽  
Mean Values ◽  
X Ray ◽  
Crystal And Molecular Structures

AbstractThe crystal structures of the compounds [R3CP(X)NR]2(R= CH3; X=S, Te for cis isomers and X= lone pair, S, Te for trans isomers) (2-6) were determined from single crystal X-ray data. The four-membered P-N rings in the cis isomers 2 and 3 show significant deviations from planarity attributed to steric overcrowding in the molecules.The trans isomers 4-6 are planar. The P-N bond lenghts (mean values for 2-6:171.4, 170, 171.6, 169.2 and 168.3 pm)in the cis isomers are not significantly different from the corresponding lengths in the trans isomers 5 and 6.

The Solid State Conformation of Diaryl Ditellurides and Diselenides: The Crystal and Molecular Structures of (C4H3E2)2E'2 (E = O, S; E' = Te, Se)

2000 ◽  
Vol 55 (5) ◽  
pp. 361-368 ◽  
Author(s):  
Raija Oilunkaniemi ◽  
Risto S. Laitinen ◽  
Markku Ahlgrén
Keyword(s):  
Solid State ◽  
Lone Pair ◽  
Spectroscopic Properties ◽  
Molecular Structures ◽  
Dihedral Angles ◽  
Single Bond ◽  
Aromatic Rings ◽  
Bond Lengths ◽  
Crystal And Molecular Structures ◽  
Solid State Conformation

The crystal and molecular structures of dithienyl ditelluride (C4H3S)2Te2 (1), difuryl ditelluride (C4H3O)2Te2 (2), dithienyl diselenide (C4H3S)2Se2 (3), and difuryl diselenide (C4H3O)2Se2 (4) are reported in this paper and compared to those of other simple diaryl ditellurides and diselenides. The chalcogen-chajcogen bonds exhibit approximately single bond lengths [Te-Te = 2.7337(8) and 2.7240(4) Å in 1 and 2, respectively; Se-Se = 2.357(1) and 2.368(2) Å in 3 and 4, respectively], as do the chalcogen-carbon bond lengths [Te-C = 2.095(9) - 2.104(6) in 1 and 2.091(6) - 2.105(9) Å in 2; Se-C = 1.87(1) - 1.90(1) Å in 3 and 1.887(8) - 1.897(10) Å in 4]. The aromatic rings are disordered. The dihedral angles C-E-E-C range from 79(2) to 96(1)° are consistent with the concept of minimized p lone-pair repulsion of adjacent chalcogen atoms. The dependence of molecular parameters on the angle between the aromatic rings and the chalcogen-chalcogen bonds follow trends established previously for aromatic disulfides. Though the bond parameters and conformations of 1 - 4 are similar, the packing of the molecules is different. The two ditellurides 1 and 2 show short Te···Te contacts (3.900 - 4.002 Å in 1 and 4.060 - 4.172 Å in 2). The two diselenides 3 and 4 do not exhibit close chalcogen-chalcogen interactions. The NMR spectroscopic properties of 1 - 4 are discussed.

A Solvent-Dependent and Electrochemically Controlled Self-Assembling/Disassembling System

2003 ◽  
Vol 68 (9) ◽  
pp. 1647-1662 ◽  
Author(s):  
Valeria Amendola ◽  
Massimo Boiocchi ◽  
Yuri Diaz Fernandez ◽  
Carlo Mangano ◽  
Piersandro Pallavicini
Keyword(s):  
Equilibrium Mixture ◽  
Bidentate Ligand ◽  
Molecular Structures ◽  
The Self ◽  
Molar Ratio ◽  
Crystal And Molecular Structures ◽  
Self Assembling ◽  
Irreversible Oxidation ◽  
Irreversible Reduction ◽  
Metal Ligand

The bis-bidentate ligand R,S-1,2-diphenyl-N,N'-bis(2-quinolinemethylidene)ethane-1,2-diamine (ligand 4), containing two (iminomethyl)quinoline moieties separated by a cis-1,2-diphenylethylene spacer, forms stable complexes with both CuI and CuII. With CuII, the monomeric 1:1 complex [CuII(4)]2+ is obtained both in CH3CN and CH2Cl2. With CuI and overall 1:1 metal/ligand molar ratio, an equilibrium mixture is obtained in CH3CN, consisting of [CuI(4)2]+, [CuI2(4)2]2+ and [CuI2(4)(CH3CN)4]2+. The preponderant species is the two-metal one-ligand "open" complex [CuI2(4)(CH3CN)4]2+, in which each Cu+ cation is coordinated in a tetrahedral fashion by one (iminomethyl)quinoline unit and by two CH3CN molecules. Precipitation from the equilibrium mixture yields only crystals of [CuI2(4)(CH3CN)4](ClO4)2·2CH3CN, whose crystal and molecular structures have been determined. On the other hand, in the poorly coordinating CH2Cl2 solvent, only the dimeric helical [CuI2(4)2]2+ complex is obtained, when the overall metal/ligand 1:1 molar ratio is chosen. Addition of large quantities of acetonitrile to solutions of [CuI2(4)2]2+ in dichlorometane results in the formation of [CuI2(4)(CH3CN)4]2+, i.e. in the solvent-driven disassembling of the CuI helicate. While electrochemistry in CH3CN is poorly defined due to the presence of more than one CuI species, cyclic voltammetry experiments carried out in CH2Cl2 revealed a well defined behavior, with irreversible oxidation of [CuI2(4)2]2+ and irreversible reduction of [CuII(4)]2+ taking place at separate potentials (∆E ≈ 700 mV). Irreversibility and separation of the redox events are due to the self-assembling and disassembling processes following the reduction and oxidation, respectively.

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